NODE fabea64cRe: proliferations of voicesystems
dr261@cleveland.Freenet.Edu (Tobin T Fricke)Sat, 26 Aug 95 19:35:03 PDT
I'd have to agree with you (Ray) completely about the need for
standards for the voice internet communications software. I
think it would be best to draw up a standard and disseminate
it rather than wait for one to emerge out of a product. If
a standard is designed, it could be designed with portability
and extensions in mind, whereas if something like InternetPhone
became a de-facto standard, it would probably be more
difficult to add upon and port to alternate platforms.
--
=================================================================
Tobin Fricke, Alias Light Ray dr261@cleveland.freenet.edu
TobinTech Engineering KE6WHF Amateur Radio
The Digital Forest BBS (714) 586-6142, 28800bps
NODE b803ee04Re: proliferations of voicesystems
Thomas Grant Edwards <tedwards@src.umd.edu>Sun, 27 Aug 95 12:40:34 PDT
On Sat, 26 Aug 1995, Tobin T Fricke wrote:
> I'd have to agree with you (Ray) completely about the need for
> standards for the voice internet communications software.
There is a standards track for real-time audio and video communications.
Seems to me the hard part is defining codecs, the easy part is dropping
in crypto.
-Thomas
NODE 71d8684bRe: proliferations of voicesystems
Thomas Grant Edwards <tedwards@src.umd.edu>Sun, 27 Aug 95 14:01:11 PDT
On Sun, 27 Aug 1995, Thomas Grant Edwards wrote:
> There is a standards track for real-time audio and video communications.
> Seems to me the hard part is defining codecs, the easy part is dropping
> in crypto.
See ftp://gaia.cs.umass.edu/pub/hgschulz/rtp/draft-ietf-avt-rtp-06.txt
for more information on the RTP standard.
See ftp://gaia.cs.umass.edu/pub/hgschulz/rtp/draft-ietf-avt-profile-04.txt
for the use of RTP in video and audio conferencing. This draft
recommends the following audio encodings:
name nom. sampling rate type frame description
Hz kb/s S/F ms
_________________________________________________________________________
L8 11025 88.2 S 8-bit linear, offset
L16 48000 768 S 16-bit linear, 2's complement
L16 44100 705.6 S
L16 22050 352.8 S
L16 11025 176.4 S
G722 16000 64 S CCITT/ITU-T subband ADPCM
PCMU 8000 64 S CCITT/ITU-T mu-law PCM
PCMA 8000 64 S CCITT/ITU-T A-law PCM
G721 8000 32 S CCITT/ITU-T ADPCM
IDVI 8000 32 S Intel/DVI ADPCM [IMA]
IDVI 16000 64 S Intel/DVI ADPCM [IMA]
G723 8000 24 S CCITT/ITU-T ADPCM
GSM 8000 13 F 20 RTE/LTP GSM 06.10
1016 8000 4.8 F 30 CELP
_________________________________________________________________________
Some of these seem perfectly appropriate for 28.8 kbps transmission, even
with the overhead of a PPP dialup connection.